Loose smut

Names

Scientific Name

Ustilago nuda

Biology

Description

Loose smut occurs wherever wheat, spelt and barley are grown. The name loose smut describes the characteristic symptoms of the diseased heads as they extend from the boot in late spring. The kernels and glumes (chaff) are converted into black fungal spores which blow away, leaving only a sooty appearing rachis or spike.

The most obvious symptom is seen at heading time as the diseased heads emerge from the boot. The kernels and glumes have been converted to masses of black spores. These spores are soon blown away, leaving the rachis of the head bare.

Heads of infected plants usually emerge from the boot slightly earlier than normal. Prior to heading infected plants may have dark green, erect leaves, sometimes with chlorotic streaks. All of the floral parts of the head, except for the rachis and pericarp membrane, are invaded by mycelium of the fungus and converted into loose aggregates of smut spores (teliospores).